In Norway domestic sheep are mostly kept on mountain pastures over summer. Previous studies have shown that climate conditions affect the growth of mountain grazing lambs in contrasting ways. We analysed a data-set from the Tjøtta Research farm in northern Norway comprising weights and growth of 8696 lambs over 17 years. The lambs grazed coastal or a mountain pasture, 15 km apart. We found that the lambs grew faster when grazing the mountain pasture. Spring and integrated Normalized Difference Vegetation Index (NDVI) affected only the lambs grazing in the mountains. Winter conditions (North Atlantic Oscillation) and summer temperature had a positive effect on growth in both pastures while spring temperature and spring NDVI were important only in the mountains. The positive effect of spring NDVI suggests that the mountain pasture will produce bigger lambs under future climate warming, while the lambs on the coastal pasture will be less affected.

We study the economy and ecology of sheep farming under future climate change scenarios. The analysis is at the farm level and includes two different categories of the animals, ewes (adult females) and lambs with a crucial distinction between the outdoor grazing season and the winter indoor season. The model is formulated in a Nordic economic and biological setting. During the outdoor grazing season, animals may experience growth constraints as a result of limited grazing resources. The available grazing resources are determined by animal density (stocking rate) and weather conditions potentially affecting the weight, and hence, the value of lambs. Because empirical evidence suggests that climate changes, e.g., increased temperature, have contrasting effects on lamb weights depending on the location of the farm, the spatial effects of such changes are analyzed.

Climate warming affects the phenology, local abundance and large-scale distribution of plants and pollinators. Despite this, there is still limited knowledge of how elevated temperatures affect plant-pollinator mutualisms and how changed availability of mutualistic partners influences the persistence of interacting species. Here we review the evidence of climate warming effects on plants and pollinators and discuss how their interactions may be affected by increased temperatures. The onset of flowering in plants and first appearance dates of pollinators in several cases appear to advance linearly in response to recent temperature increases. Phenological responses to climate warming may therefore occur at parallel magnitudes in plants and pollinators, although considerable variation in responses across species should be expected. Despite the overall similarities in responses, a few studies have shown that climate warming may generate temporal mismatches among the mutualistic partners. Mismatches in pollination interactions are still rarely explored and their demographic consequences are largely unknown. Studies on multi-species plant-pollinator assemblages indicate that the overall structure of pollination networks probably are robust against perturbations caused by climate warming. We suggest potential ways of studying warming-caused mismatches and their consequences for plant-pollinator interactions, and highlight the strengths and limitations of such approaches.

A growing number of studies on naturally occurring plant species have shown that plantplant interactions for pollination vary from competitive to facilitative. In reviewing the seven published studies on how alien species can affect the pollination success in natives, we found that all authors suggest competitive effects to dominate, either through reduced pollinator visitation rates or through increased heterospecific pollination of native flowers. Although certain pollinator interactions were competitive, the reproductive output in the native species was not always reduced. This implies that natives are not pollen limited, and/or that they compensate for the loss of pollinators by other animals. However, the few studies on pollination interactions between alien and native plant species show differing results. We therefore discuss other properties that can cause aliens to be strong interactors for pollination, and can modify how alien species affect the reproductive success in natives. We also emphasize the spatial scales addressed in the reviewed studies, as alien plant species may represent valuable food resources for many pollinators. Such plant species tend to be interpreted as competitive plants for pollination, whereas we stress their facilitative ability that may occur on a landscape scale by increasing pollinator densities. Additionally, while most studies tend to work within a shorter temporal scale, the impacts of the alien plant introductionsmay differ depending on the year or seasonal time leading to the differing results reported. (c) 2007 Elsevier Ltd. All rights reserved.

4. That a structural property of an ecological network appears less prone to sampling bias is encouraging for other studies of ecological networks. This is because it indicates that the sensitivity of ecological networks properties to effects of sampling effort might be smaller than previously expected.